As windshields become more and more sloped, a wiper which is long enough to wipe a sufficient area of the windshield to comply with Federal Motor Vehicle Safety Standards (FMVSS) might be so long that it would hit an obstruction if it were made to park at its normal wiping length. This design requirement is presently particularly troublesome for the passenger's side (i.e., right) windshield wiper of a pair of wipers that move back and forth in the familiar tandem pattern. In the future, this design requirement could also become a consideration in the design of a driver's side (i.e., left) windshield wiper or a rear window windshield wiper. The obstruction for a passenger's side windshield wiper is the side edge molding of the windshield itself or another vehicle body component, such as the hood hinge. In other words, there is only so much space available along the recess just below the lower windshield edge in which to park the wiper.
A wiper which is fabricated shorter in order to be accommodated in the available wiper parking space will not be in compliance with FMVSS. More specifically, such a wiper would be too short to wipe a sufficient area of the windshield to comply with FMVSS. Besides the problem of accommodating the wiper in the limited available space, other factors, such as the effect of freezing rain,snow, or debris, must be taken into consideration in the design of hidden park wiper arrangements. Thus, wiper mechanisms for enlarged windshields in the future will be arranged with arms which extend during operation and retract when being parked. To achieve both FMVSS compliance and provide hidden park, the wiper arm should be shortened by approximately 45 mm to 75 mm when going into the hidden park position and returned to an extended length during operation.
U.S. Pat. No. 5,119,523 discloses a linkage arrangement by which the wiper blade assembly is attached to the remote end of the wiper arm for pivotal movement to extend and retract the wiper blade assembly. In this system, the force of a spring acts on the linkage arrangement thereby causing the wiper blade to achieve its extended position during the normal wipe pattern. As the wiper blade is restored to its hidden park position, an external striker plate exerts a force on the linkage arrangement in a direction opposite to the direction of the force of the spring. In this way, the wiper blade assumes its retracted position.